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mtd: map_rom: Support UBI on ROM 

UBI needs to know the physical erase block size, even on read-only
devices, since it defines the on-device layout. Use a device-tree
provided value to support previously written UBI on read-only NOR.

UBI also needs a non-zero writebufsize, so we set it to one.

Note: This was implemented because hardware write-protected CFI
      NOR cannot be probed for the physical erase block size.

Signed-off-by: Joe Schultz <jschultz@xes-inc.ccom>
Signed-off-by: Aaron Sierra <asierra@xes-inc.ccom>
[Brian: removed unneeded #ifdef, note 'optional' erase-size property]
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
This commit is contained in:
Aaron Sierra 2014-09-25 12:20:24 -05:00 committed by Brian Norris
parent 3fc1cf5f0a
commit 6958024ad5
2 changed files with 17 additions and 1 deletions
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5
Documentation/devicetree/bindings/mtd/mtd-physmap.txt
View File

@ -36,6 +36,11 @@ are defined:
- vendor-id : Contains the flash chip's vendor id (1 byte).
- device-id : Contains the flash chip's device id (1 byte).
For ROM compatible devices (and ROM fallback from cfi-flash), the following
additional (optional) property is defined:
- erase-size : The chip's physical erase block size in bytes.
The device tree may optionally contain sub-nodes describing partitions of the
address space. See partition.txt for more detail.

13
drivers/mtd/chips/map_rom.c
View File

@ -11,6 +11,7 @@
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/of.h>
#include <linux/mtd/mtd.h>
#include <linux/mtd/map.h>
@ -28,6 +29,15 @@ static struct mtd_chip_driver maprom_chipdrv = {
.module = THIS_MODULE
};
static unsigned int default_erasesize(struct map_info *map)
{
const __be32 *erase_size = NULL;
erase_size = of_get_property(map->device_node, "erase-size", NULL);
return !erase_size ? map->size : be32_to_cpu(*erase_size);
}
static struct mtd_info *map_rom_probe(struct map_info *map)
{
struct mtd_info *mtd;
@ -47,8 +57,9 @@ static struct mtd_info *map_rom_probe(struct map_info *map)
mtd->_sync = maprom_nop;
mtd->_erase = maprom_erase;
mtd->flags = MTD_CAP_ROM;
mtd->erasesize = map->size;
mtd->erasesize = default_erasesize(map);
mtd->writesize = 1;
mtd->writebufsize = 1;
__module_get(THIS_MODULE);
return mtd;